Beam structures

ABSTRACT

A beam structure for a viaduct comprises hollow beams of reinforced concrete which are joined in end to end relationship. The end portion of each beam has an internally extending flange in which the reinforcing members of the beam are anchored. Adjacent beams are inter-connected by reinforcing cables extending across the joined ends and embedded in the adjacent flanges of the beams. The reinforcing cables and members together act to place each flange under compression. A hardenable mass injected between adjacent beams is also placed under compression by the reinforcing cables joining the two beams and provides a continuous beam structure.

[451 July 1, 1975 United States Patent 1191,,

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Related U S Applicafion Data Attorney, Agent, or Firm-McG1ew and TuttleDivision of Ser. No. 276,022, July 28, 1972, Pat. No. 3,788,023.

ABSTRACT A beam structure for a viaduct comprises hollow beams ofreinforced concrete which are joined in end [30] Foreign ApplicationPriority Data Aug. 2, 1971 9633/71 to end relationship. The end portionof each beam has an internally extending flange in which the reinforcingmembers of the beam are anchored. Adjacent beams are inter-connected byreinforcing cables extending across the joined ends and embedded in theadjacent flanges of the beams. The reinforcing cables and memberstogether act to place each flange under compression. A hardenable massinjected between adjacent ssion by the rein- [56] References CitedUNITED STATES PATENTS beams is also placed under compre forcing cablesjoining the two bea continuous beam structure.

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O O O O O XXXXXXXXM Fig.12

BEAM STRUCTURES CROSS-REFERENCE TO RELATED APPLICATIONS This applicationis a division of application Ser. No. 276,022, filed July 28, I972, andnow US. Pat. No. 3,788,023, issued .Ian. 29, 1974.

FIELD AND SUMMARY OF THE INVENTION The present invention relates to beamstructures for use in bridges and viaducts for example.

The invention provides a beam structure, for bridges and viaducts, andlike structures, comprising a plurality of beams of prestressedreinforced concrete lying in end to end relationship, and a rigidjunction between each pair of adjacent end portions of the beams to makethe structure continuous.

The invention further provides a beam structure comprising two beamslying in end to end relationship, with each beam having elongatereinforcing members extending under tension between opposite endportions. and reinforcing means coupling the adjacent end portions ofthe two beams under tension, the reinforcing members and reinforcingmeans in each adjacent end portion overlapping one another and beinganchored at axially spaced locations in the end portion to place undercompression that portion of the beam lying between the anchorings.

BRIEF DESCRIPTION OF THE DRAWINGS Beam structures embodying theinvention will now be described. by way of example, with reference tothe accompanying diagrammatic drawings in which:

FIG. I is a fragmentary longitudinal section of a beam structure, thesection being taken on the line II of FIG. 2;

FIG. 2 is a fragmentary longitudinal section taken on the line IIII ofFIG. 1;

FIG. 3 is a fragmentary cross-section taken on the line llIIII of FIG.1;

FIG. 4 is a detail of FIG. 2 to an enlarged scale;

FIGS. 5 and 6 are fragmentary side elevations of a viaduct structurerespectively during and after its erectron;

FIGS. 7 and 8 are fragmentary side elevations of another viaductstructure respectively during and after its erection;

FIG. 9 is a fragmentary side elevation indicating one form of junctionbetween two beams;

FIG. 10 is a fragmentary side elevation indicating another form ofjunction between two beams.

FIG. 11 illustrates zones between adjacent beams into which a hardenablemass can be injected.

FIG. 12 is a side elevation of the viaduct of FIGS. 7 and 8 illustratinghow a beam is fitted into position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 to 4, twobeams I and 3 are coupled in end to end relationship. The end portion ofthe beam 3 has a step 3A which supports a step 1A of complementary shapein the adjacent end portion of the beam 1. The end faces of the adjacentend portions of the beams define a gap to allow a limited amount ofrelative longitudinal movement between the beams while the two steps 1A.3A are in intimate contact with one another. The two beams areprefabricated and each has a hollow, that is an annular, cross-section(see FIG. 3) with laterally extending flanges 3B, 3C as for a viaduct.The flanges 3B and 3C are arranged so that they can be continuouslyjoined to parallel beams of similar structure extending along oppositesides of the beam 3. The internal cavity of each beam enables the twobeams l and 3 to be readily anchored in end to end relationship.

Each beam is provided with a plurality of precompression cables. In thebeam 1 a plurality of cables 5 extending the length of the beam 1 areanchored at opposite ends to corresponding opposite end portions orheads of the beam 1. In the beam 3 a plurality of cables 7 extending thelength of the beam 3 are anchored at opposite ends to correspondingopposite end portions or heads of the beam 3.

Each end portion of each beam is provided with a relatively thickinternally extending flange, the dimension of the flange in the axialdirection of the structure being greater than that in the transversedimension. The end flange 9 of the beam 1 lies adjacent the end flangell of the beam 3. The concrete material forming the two flanges 9 and 11(which flanges are advantageously stepped in conformity with the steppedend portions of the two beams) is arranged to retain coupling cables I3designed to operate in traction. The opposite end portions 13A and 13Bof each cable (like the precompression cables) are anchored on the innersurfaces of the respective flanges 9 and 11. Before the cables 13 aretensioned, a hardenable mass, for example concrete or an epoxy resin, isinjected into the gap between the adjacent heads of the two beams l and3 to form a shim 15. This shim 15 is, after it has been allowed toharden, subjected to compression by tensioning the cables l3. This alsoresults in the material of the flanges 9 and 11 being subjected tocompression. The axial thickness of the flanges 9 and 11 and theanchoring of the end portions 13A of the coupling cables 13 and the endportions 5A and 7A of the precompression cables 5 and 7 are such thatthey produce a compression effect on the material between theanchorings, as indicated by the double arrowfl of FIG. 4. In this way,the material of the flanges 9 will be subjected to substantially onlycompressive stresses which act barycentrically to reduce hyperstatic orredundant reactions.

In order to decrease the number of the coupling cables l3 and tomaintain the hardened mixture 15 under a relatively high compressivestress, the cross-sectional area of the hardened mixture I5 can bereduced to that designated in 15X in FIG. 4. The mixture here occupies across-sectional area equivalent to that of the adjacent beam beyond theflanges. This reduction in the crosssectional area enables a goodefficiency for the flexure actions to be obtained while using only arelatively small number of coupling cables 13. These cables then can beprotected by putty injected into the residual space 15Y (see FIG. 4)after the beams have been coupled and placed under stress.

FIGS. 5 and 6 show a viaduct structure having two adjacent supportingposts or piers 21 and 23 and a beam 25 partially supported by the pier21.

As shown in FIG. 5 a prefabricated beam 27 is about to be laid onto thepier 23 with its end portion 27A about to rest on the end portion 25A ofthe beam 25. Once the two end portions 25A, 27A are brought into contactthey are axially coupled in the hereinbefore described manner eitherimmediately after the beam 27 is in position as shown in FIG. 6 or, andadvantageously, after a delay which allows the complete relaxation ofthe steel of the precompression cables and the shrinkage and fluage ofthe concrete to take place.

In another viaduct structure shown in FIGS. 7 and 8, two adjacent piers31 and 33 each carry a beam 35. The two beams 35 are arranged to belinked by beam 37. The beams 35 are designed so as to take predominantlynegative moments, while the beam 37 is designed so as to takepredominantly positive moments, the precompression cables beingcorrespondingly arranged between adjacent end portions of the beams.

In the construction of the viaduct after the beam 37X which extendsbetween the beam 35X in the pier 31 and its adjacent beam on thepreceding pier (not shown) has to be located in position (by a procedureto be described for the subsequent beam), the beam 35Y is laid in abalanced condition on the pier 33. The beam is temporarily secured tothe pier by a tie-rod 39. Then the beam 37Y is launced into positionwith one end portion 37A engaging the end portion 35A of the beam 35Y,and with its other end portion 378 engaging the end portion 35B of thebeam 35X. After the launch, the beams 37Y and 35Y are coupled bycoupling cables extending through the flanges of the beams. Thereafterthe fluage of the concrete is allowed to settle and shrink before thecoupling cables are tensioned to place the concrete under stress. Thesubsequent spans are formed in the same manner.

In FIG. 9 shows a section through a modified junction between two beamswhich allows a temporary seal between the two beams to be readilydemolished, and replaced by a more permanent seal after the structurehas been allowed to settle and the stresses reach a state ofequilibrium.

As shown in FIG. 9, the adjacent end faces 41 of the two beams areinclined with respect to the vertical so as to define a gap whichdiverges with increasing distance from the common longitudinal axis ofthe beams. Spacers 43 of a detachable material (such as metal sheets,layers of synthetic resin, or artificial rubber and neoprene) aremounted on each end face 41 and a mass 45 is cast in the gaps betweenthe spacers 43 to form a temporary seal between the beams. When the masshas hardened, it is placed under compression by tensioning the couplingcables 47 which extend through the adjacent flanges of the two beams. Inthis manner, the structure is made continuous. After a delay duringwhich settlement has had time to take place, the coupling cables areloosened and the sealing 45 is removed. This is readily accomplishedbecause of the presence of the spacers 43 and because the sealing massis wedge-shaped, the mass can be removed in complete blocks with the aidof jacks or the like, or it can be broken in to fragments and removedfragment by fragment. A fresh hardenable mass is then injected betweenthe beams.

In the modified junction between two beams shown in FIG. 10, theconcrete mass is formed with the aid of a mold of plastic or othermaterial which has been lowered into the gap between adjacent end faces51 of two beams. The mold has two flanges which are arranged to engagethe end faces 51 to form gaps between the side walls of the mold and theend faces 51. Concrete is thereupon cast both into the gaps between thewalls of the mold and the end faces 51 to form blocks 55 and is alsocast into the mold 53 itself to form an additional block 57. Aftersufficient time has been allowed for settling, the coupling cables 59are loosened and the mold 53 together with the block 57 are removed toleave the blocks 55 in position. The mold 53 can thereafter bedemolished. Thereafter the remaining gap between the beams is sealed ina more permanent manner.

In this manner it is possible both to assure the immediate continuity ofthe launched structure and to subsequently relieve the over-stressesproduced by casting the temporary concrete blocks before the completestructure has had time to settle.

The temporary sealing such as the ones denoted by 45 or 57 respectivelyin FIGS. 9 and 10 can advantageously be provided in the zone 61 or thezone 63 of the beam as indicated in FIG. 11.

An advantage of providing a temporary seal between beams is that theresulting continuous structure formed can be used almost straight awayto carry new beams to be added to the structure into their requiredpositions. This simplifies and speeds constructional operations sincethe launching bridge need not be made to traverse all the piers in orderto pick up fresh beams from one end of the structure but can remain in aposition where it is required, that is, at the end of the thus farcompleted structure.

In the construction ofa continuous beam structure as indicated in FIG.12, lifting equipment 65 for lifting successive beams into position hasone leg mounted on the over-hang portion 61X of the completed length ofthe continuous beam 61 and its other leg mounted on a subsequent pier67. Prefabricated beams 69 and 71 are conveyed along the completedlength of the continuous beam 61 until they reach the equipment 65,whereupon the beam 69 is raised by the equipment and laid onto the pier67 as indicated by broken lines 69X. Thereafter the beam 71 is raised bythe equipment and laid between the beam 69 and the over-hang 61X.

The two beams 69 and 71 are then coupled by coupling cables as is thebeam 71 with the over-hand portion 61X. Thereafter temporary casings aremade at the beam junctions.

It will be appreciated that because the temporary casting is readilyremovable (which casting provides an initial continuity of the beamstructure with the associated advantages) the resultant stressesresulting from settlements of the bonds, fluage of the concrete andrelaxation of the steel cables can be readily relieved.

This continuous beam structure is particularly advantageous where thecontinuous beam structure has to follow a curved path and also forbridging spans in excess of 30 to 40 linear meters and up to I00 linearmeters.

I claim:

1. A beam structure, comprising two beams means supporting the two beamsin end to end relationship, each beam having elongate reinforcingmembers extending under tension between opposite end portions,reinforcing means coupling the adjacent end portions of the two beamsunder tension, the reinforcing members and reinforcing means in eachsaid adjacent end portion overlapping one another, and

means anchoring the reinforcing members and reinforcing means at axiallyspaced locations in the end portion to place under compression thatportion of the beam lying between the anchorings.

flanges are internal of the beam.

5. A structure according to claim 2, including a hardened meansextending between the adjacent end portions of the beams, the hardenedmass being subjected to a compression force by the reinforcing means.

6. A structure according to claim 5, wherein the hardened mass has across-sectional area smaller than that of the flanges.

1. A beam structure, comprising two beams means supporting the two beamsin end to end relationship, each beam having elongate reinforcingmembers extending under tension between opposite end portions,reinforcing means coupling the adjacent end portions of the two beamsunder tension, the reinforcing members and reinforcing means in eachsaid adjacent end portion overlapping one another, and means anchoringthe reinforcing members and reinforcing means at axially spacedlocations in the end portion to place under compression that portion ofthe beam lying between the anchorings.
 2. A beam structure according toclaim 1, wherein each end portion of the beam has a flange to which theanchoring means are secured, each flange having a dimension in the axialdirection of the structure which is greater than that in the transversedirection of the structure.
 3. A structure according to claim 2, whereineach beam is of hollow cross-section.
 4. A structure according to claim3, wherein the flanges are internal of the beam.
 5. A structureaccording to claim 2, including a hardened means extending between theadjacent end portions of the beams, the hardened mass being subjected toa compression force by the reinforcing means.
 6. A structure accordingto claim 5, wherein the hardened mass has a cross-sectional area smallerthan that of the flanges.